NK cells in the infected cecal mucosa of IL-18-deficient mice are phenotypically immature.

(a and b) Flow cytometric analysis of isolated cecal LP cells from Sm-pretreated C57BL/6 WT mice, either uninfected or infected with 5x10⁷ CFU S.Tm (n = 5 per group). We gated on single live CD45⁺ CD3^- NK1.1⁺ cells. (a) Representative contour plots and (b) quantification of NK cell maturation stages, defined by the surface expression of CD27 and CD11b; arrows indicate the progression of NK-cell maturation. (c and d) Flow cytometric analysis of isolated cecal LP cells from Il18^-/- mice and littermates, Sm-pretreated and orally infected with 5x10⁷ CFU S.Tm for 12h (n = 5–6 per group). We gated on single live CD45⁺ CD3^- NK1.1⁺ cells. (c) Representative contour plots and (d) quantification of NK cell maturation stages based on CD27 and CD11b surface expression. Data represent the mean ± SD and statistical analyses were performed using 2way-ANOVA with Sidak’s multiple comparison test (ns = not significant, * = p<0.05; ** = p<0.01; *** = p<0.001).